Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$92.57	6.813%	$98.8768	$98.88	$98.90	$98.90
Purchase #2	$59.61	7.266%	$63.9413	$63.94	$63.95	$63.90
Purchase #3	$78.28	12.493%	$88.0595	$88.06	$88.05	$88.10
Purchase #4	$157.66	13.275%	$178.5894	$178.59	$178.60	$178.60
Purchase #5	$183.57	3.383%	$189.7802	$189.78	$189.80	$189.80
Purchase #6	$178.33	10.290%	$196.6802	$196.68	$196.70	$196.70
Purchase #7	$227.72	12.699%	$256.6382	$256.64	$256.65	$256.60
7 purchase totals =	$977.74		$1,072.5656	$1,072.57	$1,072.65	$1,072.60